torque loss with e-cutout open?

[TraceZ]

I love the sound of my Borla with the cutout open so much that I have not closed it much at all. It's been pretty much open constantly.

I've always known that would cost me a little low end torque, but never really tested it out.

Today, I drove to work and back with it closed, and what a difference it makes! I was getting rubber where I wouldnt have been with the cutout open. It is a piece of cake to take a corner sideways by just touching the gas.

This got me thinking about the new Corvette Z06 with its computer controlled e-cutout. I'm guessing that remains closed at low RPM and opens up at high RPM. Nice thinking, Chevy!

[AmericanZ28]

I had a similar experience back when I had my cut out, but I thought it was just the noise creating the illusion of less low end torque. Did you notice much of a SOTP difference between closed and open? With regards to the new Z06, I thought the cut out worked with exhaust pressure rather than a computer controlled motor. You sure its computer controlled?

[TraceZ]

I had a similar experience back when I had my cut out, but I thought it was just the noise creating the illusion of less low end torque. Did you notice much of a SOTP difference between closed and open? With regards to the new Z06, I thought the cut out worked with exhaust pressure rather than a computer controlled motor. You sure its computer controlled?

I guess I was assuming the Z06 valve was computer controlled... I'm not sure if that is true. But, the difference in low end torque with the valve shut is noticable to the degree the car feels seriously more powerful. I was spinning the tires left and right on the way home. It was a blast. I suppose it could of been a combination of the cold air (40f) cold tires and extra torque. Whatever it was, the car felt really strong.

I got this from another forum:

there is a vacuum tank at the rear of the car,.vacuum motors actuate the valves...there must also be a pcm controlled vacuum solenoid to switch the vacuum to the motors...that solenoid is where i think the mod can be made to manually overide the system.....

so it looks like it is PCM controlled via vacuum switches.

[Craig 94 TA GT]

Up to what RPM do you notice a difference? Although something was terribly wrong with my car when dynoed, I saw only a 0.33 ft-lb torque difference at 3750 and beyond with the cutout opened compared to closed...with a full exhaust. To be honest, I've heard this from many, but never noticed it at all.

[fastTa]

I suppose it could of been a combination of the cold air (40f) cold tires and extra torque. Whatever it was, the car felt really strong.

That was likely what it was. Cold dense air can really make a big difference in power.

[Joe 1320]

That was likely what it was. Cold dense air can really make a big difference in power.

And cold pavement also makes the traction go away.

[TraceZ]

Ok guys, thanks for the replies. I'm thinking it was the 40f air combined with less traction due to the cooler road surface. I had to drive the minivan to work today because I have the kids to dropoff / pickup at daycare. I'm second guessing myself now, but I'm telling ya, it really felt more powerfull. I wish I could drive it more today to play around with it, I dont get chances to drive it but a couple days a week and it will be going up for winter storage in a few more weeks.

And, to answer your question Craig, I noticed the power increase from 1000 - 3000 RPM. Above that, it felt about the same to my a$$ometer. It was like an extra kick in the pants from a stop. It made the car feel really responsive to pedal input.

[Joe 1320]

Part of that is due to the IAT reading a colder temperature and allowing a faster timing advance rate. Cooler air does affect performance in a good way!

[TraceZ]

Part of that is due to the IAT reading a colder temperature and allowing a faster timing advance rate. Cooler air does affect performance in a good way!

I have my IAT bypassed with the "resistor mod". The colder denser air could still make a difference, but this was really a SOTP difference. I'm thinking it must of been a combination of factors.


Another thing I've been noticing is my clutch feels like it has not been grabbing as hard as it should. But, on the drive yesterday it seemed to be grabbing harder. Maybe that made for better torque transfer to the rear wheels. I installed this clutch 2 years ago, but have not put more than a few thousand miles on the car since. Maybe it is just breaking in? The clutch engages very high on the pedal. to disengage it I only have to push the pedal a couple inches.

It's too many variables for me to pinpoint the cause, but man, I tell you that car was alive yesterday and now I'm stuck with the minivan today.